Process for Preparing Ammonic Glyphosate Granules

ABSTRACT

A process for preparing water-soluble granules of amnionic glyphosate comprising: a) addition of glyphosate acid to a Broensted base which supplies ammonium ions in a molar ratio base/acid comprised between 0.8 and 1.1; b) homogenization of the mixture prepared in a); c) addition of one or more surfactants in amounts in the range 5%-50% by weight based on the glyphosate acid; d) mixing of the mass prepared in c) for a time lower than about 10 minutes until obtaining an extrudable mass; e) extrusion of the mass obtained in d); f) drying until obtaining a granule having a residual moisture lower than 1%.

The present invention relates to a process for preparing water-solublegranules ammonic glyphosate-based to be used in the agrochemical field.

The glyphosate (N-phosphonomethyl glycine) is well known in the priorart as a compound having an herbicide activity effective for the weedcontrol. It is also known that the glyphosate, being an organic acid notsoluble in water, must be converted into its salts to allow the usethereof. The most commonly used salts are the isopropylamine salt, sodicsalt and ammonic salt. The isopropylamine salt is formulated andmarketed under the form of concentrated aqueous solution. However theneed to save money in the manufacturing, transportation and packingdisposal costs has recently brought to consider solid formulations, inparticular under the form of granules.

The sodic salt and the ammonic salt are particularly suitable towater-soluble granules formulation, more particularly the ammonicglyphosate as less hygroscopic and thus more resistant in moistenvironment and besides more effective from the biological point ofview.

With the ammonic glyphosate term it is meant the glyphosate monoammonicsalt.

The water-soluble glyphosate granules can be prepared with variousprocesses.

For example, a known process comprises the salification step of theglyphosate acid with a base, optional addition of other coformulatingagents as surfactants, inert agents, antifoam agents and a subsequentgranulation step by known techniques in the art as extrusion,agglomeration, preferably extrusion (see for example U.S. Pat. No.5,633,397).

Another process comprises the mixing step of the glyphosate acid, of thebase, of the optional coformulating agents, and the salification step inan extruder (see for example U.S. Pat. No. 5,070,197).

Another process describes the mixing under anhydrous conditions of theglyphosate acid in powder form with a suitable solid base, for examplesodium acetate, with no salification reaction; the latter taking placeonly when the granule is poured into water before the use (see forexample WO 92/12,637).

The salification of the glyphosate acid, when required, can be carriedout with various methods. In particular the ammonic glyphosate can beprepared by using anhydrous or aqueous solution ammonia, as salificationbase, by using processes comprising mixing, reaction and extrusion in asingle step (see for example U.S. Pat. No. 5,070,197), or processesincluding separate steps (see for example U.S. Pat. No. 5,633,397 andU.S. Pat. No. 6,734,142).

The processes using ammonia, show the advantage of being carried out ina continuous way due to the high reaction rate solid-gas andsolid-liquid. However they suffer the following drawbacks. The anhydrousammonia is a toxic gas whose use in safety conditions requires specificprecautions not usually available in agrodrug formulation plants. Theammonia in aqueous solution is corrosive and also difficult to be safelyhandled. In both cases the salification by using ammonia results to bestrongly exothermic. For these reasons expensive technical precautionsin the plant for the process management and for the operator safety mustbe foreseen as, for example, temperature controls, cooling circuits andsafety systems.

A further drawback is noted in single step processes as the equipmentsrequired for this kind of process are extruders normally used in theplastic material extrusion, for example high pressure screw extruders,wherein the temperature rises to levels so to make particularlydifficult the choice of coformulating agents, in particular of thesurfactant. Processes of this kind, requiring the salification in theextruder, have never been described in low pressure extruders usuallyutilized to produce water soluble or dispersible granules in theagrochemical field. This is likely due to the different configurationand different characteristics of a low pressure extruders compared tohigh pressure extruders.

The above drawbacks can be overcome by using bases under the solid form,for example ammonium bicarbonate, instead of the ammonia (see forexample U.S. Pat. No. 6,228,807). However these processes show thedrawback to require a particularly long preparation step of the mass tobe extruded: this step in fact requires the complete salification of theglyphosate acid and this takes place in a time of at least 20-30minutes. Said characteristic negatively affects the productivity ofthese processes, a configuration of the salification zone in acontinuous way not being achievable. Besides, the salification step caninfluence the consistence of the mass to be extruded and theincorporation of the surfactant in the formulation.

As known, the surfactants have the purpose to favour, at the time of theuse, the glyphosate herbicide effectiveness by acting on the permanenceof the drop on leaves, on the adhesion of said drops to the leaf surfaceand on the penetration of the active principle through the cuticle.

It is desirable that in the final formulation the surfactant, acting asan adjuvant, is present in amounts in the range 5%-35% by weight withrespect to the glyphosate, expressed in equivalent acid. However an easyincorporation of high amounts of surfactant only takes place when theformulations have a low glyphosate content. On the other hand, in orderto decreasing the manufacturing, the granule transportation and thepacking disposal costs, solid products are required more concentrated inglyphosate, making more difficult the incorporation of high amounts ofsurfactant. As a matter of fact a high concentration of surfactant ishardly adsorbed/absorbed by the mass containing glyphosate, making theprocessing thereof difficult, especially in case of low pressureextrusion.

Processes preparing ammonic glyphosate capable of containing highsurfactant amounts are known. However these processes use anhydrousammonia (see for example U.S. Pat. No. 5,633,397) or ammonia in aqueoussolution (see for example U.S. Pat. No. 6,605,568 and U.S. Pat. No.5,716,903) and therefore with the above technical drawbacks.

Processes for preparing granular compositions not requiring thesalification step are known. For example WO 92/12,637 requires themixing under anhydrous conditions of the glyphosate acid under thepowder form with a suitable solid base without any salification reactiontakes place which arises only when the granule is poured in water beforethe use. This process, even though it does not involve any salificationstep, shows however the drawback of being carried out in a completelyanhydrous environment, in case of the soluble glyphosate salts, in ordernot to cause the salification reaction before the use.

The need was felt to have available a process for preparing ammonicglyphosate granules showing the following combination of properties:

-   -   no use of anhydrous ammonia or in aqueous solution;    -   having a preparation step of the extrudable mass lower than 20        minutes, preferably lower than 10 minutes, and therefore with a        high productivity;    -   carried out also in a continuous way;    -   allowing to obtain an extrudable mass in low pressure extruders;    -   capable of incorporating in the granule formulation a high        surfactant amount in combination with a high glyphosate amount.

It has surprisingly and unexpectedly found that the preparation ofammonic glyphosate granules with the process described hereinafterallows to solve the above technical problem.

It is therefore an object of the present invention a process forpreparing water-soluble ammonic glyphosate granules comprising:

-   a) addition of glyphosate acid, under the wet cake form, to a solid    Broensted base, which supplies ammonium ions, in amounts equal to a    molar ratio base/acid between 0.8 and 1.1, preferably between 0.9    and 1.05, optionally in the presence of coformulating agents such as    inert, antifoam agents;-   b) homogenization of the mixture prepared in a);-   c) addition of one or more liquid surfactants, in amounts in the    range 5%-50% by weight, preferably 10%-40%, more preferably 12%-35%    based on the glyphosate acid;-   d) mixing of the mass prepared in c) for a time lower than about 10    minutes, preferably lower than about 5 minutes, more preferably    comprised between about 30 seconds and 3 minutes, until obtaining an    extrudable mass;-   e) extrusion of the mass obtained in d);-   f) drying until obtaining a granule having a residual moisture lower    than 1%, preferably lower than 0.5%.

In step a) wet cake means that the technical glyphosate acid in powdercontains water amounts between 5% and 20%, preferably between 10% and15%. In general the preferred water amount of the wet cake is such tolead, depending on the used formulation, to an extrudable mass havingthe consistence of a moist powder in a time lower than 3 minutes when aPloughshare type mixer, equipped with “chopper” (additional lowintensity and high shear strength mixing devices) is used.

In step a) the solid Broensted base supplying ammonium ions can be, forexample, selected from ammonium carbonate, bicarbonate, carbamate ormixtures thereof, optionally added of small amounts of antipackingagents as, for example, magnesium carbonate. Preferably the base in stepa) is an equimolar mixture of ammonium carbonate, bicarbonate,carbamate. In said solid base, if necessary, lumps, if present, arereduced or removed before adding the other components. Preferably thebicarbonate base is used in admixture with other Broensted bases.

As inert agents to be added in step a), ammonium sulphate, potassiumsulphate, sodium sulphate, preferably ammonium sulphate, can bementioned. Preferably the inert agent is milled before being added tothe other components so as to have particle size lower than 500 micron.

As antifoam agents, silicone antifoam agents can preferably bementioned. The antifoam agent can be added, alternatively, in step c)together with the surfactant.

In step b) mild stirring is generally used, usually for a time lowerthan one minute.

Homogenization is carried out, for example, in high stirring intensitystatic mixers of the Ploughshare type, optionally equipped with“choppers” or in continuous mixers having high shear strength.Preferably in this step b) the choppers are not used. Generally, in caseof Ploughshare type mixers, mild stirring means that the revolutionnumber is generally between 20 and 40 rpm.

In step c) the surfactant addition is preferably carried out under mildstirring. Stirring can be of the same type (intensity) as that used instep b).

In step c) the surfactant is, for example, selected from solid or liquidcompounds at room temperature, for example alkanol amide, betainederivative, ethoxylated-propoxylated block copolymer, glycerol ester,glycolic ester, imidazoline and its derivatives, lanolin and lecithinderivatives, tertiary and quaternary polyoxyalkylenalkyl amines,polyoxyalkylen alkylether, polyoxyalkylen alkyl aryl ether,polyoxyalkylen alkyl ester, alkoxylated and non alkoxylated sorbitanester, alkyl glycoside, alkyl polyglycoside, alkyl sulphate, alkylphosphate, sulphonated olefin, alkyl aryl sulphonate, polyoxyalkylenalkyl ether sulphate, polyoxyalkylen alkyl ether phosphate,sulphosuccinate derivative, taurate, vegetable oil sulphonate of a fatacid, of an alcohol, of an alcoholalkoxylate, of a fat acid ester, anaromatic derivative of a fat acid ester or mixtures thereof, aminederivatives of vegetable oils or of fat acids.

Preferably said surfactant is added in a liquid form to the mixtureobtained in step b).

Preferably as surfactant ethoxylated tallow amine is used, havinggeneral formula

R—N(CH₂CH₂O)H_(m)(CH₂CH₂O)H_(n)

(R=saturated alkyl chain having 16-18 carbon atoms).

Step d) is preferably carried out under stirring with higher intensitythan that of step c). In the above Ploughshare type mixers, ratesbetween about 80 and 120 rpm are generally used. Preferably in this stepchoppers are used.

In step d) the mass mixing preferably takes place in the same devicewherein the previous step c) has been carried out but increasing theshear rate so as to obtain an extrudable mass, that is a mass having aconsistence suitable to be extruded in the used extruder.

The consistence suitability mainly depends on the technology selectedfor the granulation: said consistence can range from a moist powderconsistence to a dough-like consistence; it is preferable to have aconsistence lower than the dough-like consistence.

In the particular case of granulation by low pressure extruders of theso called radial, basket or twin dome type, the suitable consistence isthat of a moist powder capable to be plastically deformed when subjectedto compression (for example in the hand palm). A suitable extruder tocarry out the process of the invention is a low pressure extruder baskettype.

Without to be bound to any theory, the Applicant keeps that the optimalconditions to carry out step d) are: mass mixing for a time sufficientto obtain an extrudable mass as defined above.

Generally, by using Ploughshare mixers at the above rates, theextrudable mass can be obtained even with times lower than one minute.

Preferably, during the time wherein step d) takes place, the temperatureremains substantially constant.

The mass obtained after the mixing d) is essentially formed of unreactedglyphosate acid, ammonic glyphosate, Broensted base. As a matter of factthe Applicant has unexpectedly and surprisingly found that thecompletion of the salification reaction is not a necessary condition forobtaining, before, an extrudable mass, and, after, a good granule basedon ammonic glyphosate.

The unreacted glyphosate acid is present in the mass obtained in d)preferably in amounts ranging from a maximum of 70% to a minimum of 10%with respect to the initial acid amount. It follows that ammonicglyphosate in a minimum molar amount of 30% and a maximum of 90% withrespect to the starting glyphosate acid and the corresponding amount ofunreacted base will be present in the extrudable mass.

The presence of unreacted glyphosate acid and thus of unreactedBroensted base in the extrudable mixture is shown from the carbondioxide development (effervescence) when a portion of the mixtureobtained in the mixing step d) is put in water. As said, during step d)the mass temperature substantially remains unchanged.

In step e) the extrusion of the mass obtained in d) is preferablycarried out by low pressure extruders and produces strings, which breakby fall in coherent and moist granules to be dried. Said granules, whenput in water, show gas development.

In step f) drying is preferably carried out in fluid bed dryers,generally at temperatures in the range 70° C.-120° C., preferably 80°C.-100° C. The drying temperature is however such as not to implydegradation or loss of surfactant or of other formulation additives.

The dried granules obtained in step f), when put in water, do not showany gas development but are completely water-soluble without carbondioxide development and without undissolved sediments. This means thatthe salification is completed during step f). The drying step generallylasts between 10 and 15 minutes or at any rate for a time such as toobtain a granule having the above characteristics when put in water, anda residual moisture lower than 1%, preferably lower than 0.5%.

The Applicant has found that with the process of the present inventionit is possible to prepare water-soluble ammonic glyphosate granules by asimple process, not requiring the use of dangerous substances, notimplying heat development, allowing the incorporation in the formulationof high amounts of surfactant. Furthermore the process of the presentinvention has realization times much lower than those of known processesrequiring the salification step. It thus follows a higher productivity,the time and the initial amount of components being equal, besides thepossibility to carry out the process of the present invention even in acontinuous way.

It has besides been found that with the process of the present inventionit is possible to remarkably increase the surfactant content in thegranule. As said above, this is a highly desired characteristic for theglyphosate granules.

The granules obtainable with the process of the invention have anequivalent glyphosate acid content higher than or equal to 48% by weightand a surfactant content in the range 5%-25% by weight, preferably10%-20% by weight.

Preferred compositions are the following (% by weight):

1. pure ammonic glyphosate 79.2 (equivalent acid 72) surfactant 10 inertagents and impurities to 100 2. pure ammonic glyphosate 79.2 (equivalentacid 72) surfactant 15 inert agents and impurities to 100 3. pureammonic glyphosate 74.8 (equivalent acid 68) surfactant 15 inert agentsand impurities to 100 4. pure ammonic glyphosate 66 (equivalent acid 60)surfactant 20 inert agents and impurities to 100

The surfactant preferably used in these compositions is tallow amine.

Some illustrative but not limitative Examples of the pre-sent inventionfollow.

EXAMPLES Characterization Determination of the Glyphosate Acid Contentin the Granule

It was determined by analytical method CIPAC 284/SG/M by using the HPLC(High Performance Liquid Chromatography) technique with ionic exchangecolumn, wave length UV 195 nm and external standard.

Determination of the pH of the Granule Dissolved in Water

It was determined by CIPAC 75 method by using a common pHmeter.

Determination of the Granule Solubility

The glyphosate granule solubility was determined by the followingmethod.

A granular product amount having a known glyphosate acid content isweighed so as to obtain 100 ml of a solution containing glyphosate acidin concentration 5 times higher than the employment dose (employmentdose=14.4 g/l). The aqueous solution is prepared by stirring for twominutes with a glass rod, the product is poured in a 100 ml graduatedconical cylinder ASTM D 96. The cylinder is then capped and turned over15 times in about ½ minute. Then the solution is allowed to rest for 1hour in a bath at a temperature of 20° C.±2. Then the presence ofpossible sediments is visually controlled with a ±0.05 ml precision.

Determination of the Residual Moisture Content of the Granule

It was determined by the CIPAC MT 30.1 method.

Example 1

2,348 grams of an equimolar mixture of ammonium carbonate, bicarbonateand carbamate, commercially known as Hartshorn salt (E503) havingammonia titre of 31%, were cleared removed from lumps in a Loedige mixer(of the Ploughshare type) equipped with chopper; 8,297 grams oftechnical glyphosate having titre 96.9% with respect to the dry productand moisture 10%, 776 grams of ammonium sulphate previously milled by arung mill were then added and mixed for one minute. While maintainingthe mixture under mild stirring, corresponding to 20 rev/minute, 1,000 gof tallow amine (surfactant) Emulson® AG/PE 3SS (corresponding to acontent of 10% by weight based on the final composition and of 13% byweight based on the acid) and 10 grams of antifoam agent Antifoam® SLwere added.

The obtained mass was then subjected to mixing at the maximum intensitycorresponding to 100 rev/minute, with the aid of a chopper for 3 minutesuntil obtaining an extrudable mixture.

The mixture had the consistence of a moist powder, deformable bycompression in a hand.

The mass temperature during said step maintained itself lower than 35°C.

Said mixture was then sent to a low pressure basket extruder having adiameter of 130 mm and a screen with 1 mm thickness and holes, andextruded.

The extruded product was then dried in a fluid bed dryer for 15 minuteswith hot air having an inlet temperature of 100° C.

The whole process was monitored by carrying out some solubility test ofthe mass to be extruded, of the extruded granule and of the driedgranule, observing development of carbon dioxide in case of theextrudable mass and of the extruded granule, and not observingdevelopment of carbon dioxide in case of the dried granule.

The latter was then characterized by carrying out the analyses describedin the characterization, obtaining the following values:

glyphosate acid content: 72% by weight;

pH: 3.9;

solubility: complete without sediments;

residual moisture: 0.5%.

Example 2

The Example 1 was repeated but by using 276 grams of ammonium sulphatepreviously milled instead of 776 grams.

While maintaining the mixture under mild stirring, corresponding to 20rev/minute, 1,500 g of tallow amine (surfactant) Emulson® AG/PE 3SS(corresponding to a content of 15% based on the dry product and of 20.8%based on the acid) and 10 grams of antifoam agent Antifoam® SL wereadded.

The obtained mass was then subjected to mixing at the maximum intensitycorresponding to 100 rev/minute, with the aid of a chopper for 3 minutesuntil obtaining an extrudable mixture.

The mixture had the consistence of a moist powder, deformable bycompression in a hand.

The mass temperature during said step maintained itself lower than 35°C.

Said mixture was then sent to the extruder described in the Example 1and extruded; the extruded product was then dried in the dryer describedin the Example 1 under the same conditions.

The whole process was monitored by carrying out some solubility test ofthe mass to be extruded, of the extruded granule and of the driedgranule, observing development of carbon dioxide in case of the mass tobe extruded and of the extruded granule, and not observing developmentof carbon dioxide in case of the dried granule.

The dried granule was then characterized by carrying out the analysesdescribed in the characterization, obtaining the following values:

glyphosate acid content: 72%;

pH: 3.9;

solubility: complete without sediments;

residual moisture: 0.5%.

Example 3

The Example 1 was exactly repeated except that the mixing of step d) wascarried out for 1 minute. The mass resulted extrudable as in the Example1 and the analyses carried out on the dried granule gave the followingvalues:

glyphosate acid content: 72%;

pH: 3.9;

solubility: complete without sediments;

residual moisture: 0.5%.

Example 4 Comparative

The Example 1 was exactly repeated except that the mixing of step d) wascarried out for about 30 minutes according to U.S. Pat. No. 6,228,807.

It has been noticed:

-   -   a temperature increase up to over 60° C., due to the friction        inside the mixer;    -   the complete salification of the glyphosate acid;    -   the non extrudability of said mass.

Furthermore also the subsequent cooling of the mass up to roomtemperature by flowing of water in the jacket, carried out in 30minutes, has not allowed to obtain an extrudable mass.

Example 5 Comparative

The Example 1 was repeated except that 1,776 grams of ammonium sulphatewere used and no surfactant was used.

Mixing was carried out at the maximum intensity, corresponding to 100rev/minute, with the aid of a chopper for 3 minutes; under theseconditions it was not possible to obtain an extrudable mixture.

The mass temperature during said step maintained itself lower than 35°C.

Example 6 Comparative

The Example 1 was repeated but in the absence of inert agent, surfactantand antifoam agent.

The base and the acid were subjected to mixing at the maximum intensitycorresponding to 100 rev/minute, with the aid of a chopper for 3minutes; under these conditions it was not possible to obtain anextrudable mixture.

The mass temperature during said step maintained itself lower than 35°C.

Example 7 Comparative

The Example 1 was repeated but by using 1,476 grams of ammonium sulphatemilled as in the Example 1 and 300 g of tallow amine (surfactant)Emulson® AG/PE 3SS (corresponding to a content of 3% with respect to thefinal composition and of 4.2% with respect to the acid).

The obtained mass was then subjected to mixing at the maximum intensity,corresponding to 100 rev/minute, with the aid of a chopper for 3minutes.

The obtained mass did not result extrudable in the extruder described inthe Example 1.

Example 8

2,257 grams of an equimolar mixture of ammonium carbonate, bicarbonateand carbamate, commercially known as Hartshorn salt (E503) havingammonia titre of 31%, were cleared from lumps in a Loedige mixer(Ploughshare type) equipped with chopper; 7,976 grams of technicalglyphosate having titre 96.9% and moisture 10%, 917 grams of ammoniumsulphate previously milled by a rung mill were then added and mixed forone minute.

While maintaining the mixture under mild stirring, corresponding to 20rev/minute, 1,500 g of tallow amine (surfactant) Emulson® AG/PE 3SS(corresponding to a content of 15% based on the final composition and of22% based on the acid) and 10 grams of antifoam agent Antifoam® SL wereadded.

The obtained mass was then subjected to mixing at the maximum intensity,corresponding to 100 rev/minute, with the aid of a chopper for 3 minutesuntil obtaining an extrudable mixture.

The mixture had the consistence of a moist powder, deformable bycompression in a hand.

The mass temperature during said step maintained itself lower than 35°C.

Said mixture was then sent to the extruder described in the Example 1and extruded. The extruded product was then dried in the dryer of theExample 1 and under the same conditions.

The whole process was monitored by carrying out some solubility test ofthe mass to be extruded, of the extruded granule and of the driedgranule, observing development of carbon dioxide in case of the mass tobe extruded and of the extruded granule, and not noticing development ofcarbon dioxide in case of the dried granule.

The dried granule was then characterized by carrying out the analysesdescribed in the characterization, obtaining the following values:

glyphosate acid content: 68%;

pH: 3.9;

solubility: complete without sediments;

residual moisture: 0.5%.

Example 9

1,957 grams of an equimolar mixture of ammonium carbonate, bicarbonateand carbamate, commercially known as Hartshorn salt (E503) havingammonia titre of 31%, were cleared from lumps in a Loedige mixer(Ploughshare type) equipped with chopper; 6,914 grams of technicalglyphosate having titre 96.9% and moisture 10%, 1,145 grams of ammoniumsulphate previously milled by a rung mill were then added and mixed forone minute.

While maintaining the mixture under mild stirring, corresponding to 20rev/minute, 2,000 g of tallow amine (surfactant) Emulson® AG/PE 3SS(corresponding to a content of 20% based on the final composition and of33.3% based on the acid) and 10 grams of antifoam agent Antifoam® SLwere added.

The obtained mass was then subjected to mixing at the maximum intensity,corresponding to 100 rev/minute, with the aid of a chopper for 3 minutesuntil obtaining an extrudable mixture.

The mixture had the consistence of a wet powder, deformable bycompression in a hand.

The mass temperature during said step maintained itself lower than 35°C.

Said mixture was then sent to the extruder described in the Example 1and extruded; the extruded product was then dried in the dryer of theExample 1 and under the same conditions.

The whole process was monitored by carrying out some solubility tests ofthe mass to be extruded, of the extruded granule and of the driedgranule, observing development of carbon dioxide in case of the mass tobe extruded and of the extruded granule, and not noticing development ofgas in case of the dried granule.

The dried granule was then characterized by carrying out the analysesdescribed in the characterization, obtaining the following values:

glyphosate acid content: 60%;

pH: 3.9;

solubility: complete without sediments;

residual moisture: 0.5%.

The obtained granule shows a high concentration of glyphosate acid incombination with a high concentration of surfactant, whose ratio iscomparable to that found in commercial products having a lowerglyphosate titre, for example granules containing 36% by weight ofglyphosate.

1. A process for preparing water-soluble ammonic glyphosate granulescomprising: a) addition of glyphosate acid, under wet cake form, to asolid Broensted base, which supplies ammonium ions, in amounts equal toa molar ratio base/acid between 0.8 and 1.1, preferably between 0.9 and1.05, optionally in the presence of coformulating agents such as inert,antifoam agents; b) homogenization of the mixture prepared in a); c)addition of one or more liquid surfactants, in amounts in the range5%-50% by weight, preferably 10%-40%, more preferably 12%-35% based onthe glyphosate acid; d) mixing of the mass prepared in c) for a timelower than about 10 minutes, preferably lower than about 5 minutes, morepreferably comprised between about 30 seconds and 3 minutes, untilobtaining an extrudable mass; e) extrusion of the mass obtained in d);f) drying until obtaining a granule having a residual moisture lowerthan 116, preferably lower than 0.5%.
 2. A process according to claim 1,wherein the Broensted base of step a) is selected from ammoniumcarbonate, bicarbonate, carbamate or mixtures thereof, optionally addedof small amounts of antipacking agents as, for example, magnesiumcarbonate.
 3. A process according to claim 2, wherein the base is anequimolar mixture of ammonium carbonate, bicarbonate, carbamate.
 4. Aprocess according to claims 1, wherein the inert agents of step a) areselected from ammonium sulphate, potassium sulphate, sodium sulphate,preferably ammonium sulphate.
 5. A process according to claims 1,wherein the antifoam agent is a silicone antifoam agent.
 6. A processaccording to claims 1, wherein the step b) takes place under mildstirring, preferably in a mixer working at a revolution number between20 and 40 rpm.
 7. A process according to claims 1, wherein thesurfactant addition of step c) takes place under mild stirring,preferably in a mixer working at a revolution number between 20 and 40rpm.
 8. A process according to claims 1, wherein the surfactant isselected from solid or liquid surfactants at room temperature,preferably from alkanol amide, betaine derivative,ethoxylated-propoxylated block copolymer, glycerol ester, glycolicester, imidazoline and its derivatives, lanolin and lecithinderivatives, tertiary and quaternary polyoxyalkylenalkyl amines,polyoxyalkylen alkylether, polyoxyalkylen alkyl aryl ether,polyoxyalkylen alkyl ester, alkoxylated and non alkoxylated sorbitanester, alkyl glycoside, alkyl polyglycoside, alkyl sulphate, alkylphosphate, sulphonated olefin, alkyl aryl sulphonate, polyoxyalkylenalkyl ether sulphate, polyoxyalkylen alkyl ether phosphate,sulphosuccinate derivative, taurate, vegetable oil sulphonate of a fatacid, of an alcohol, of an alcoholalkoxylate, of a fat acid ester, anaromatic derivative of a fat acid ester or mixtures thereof, aminederivatives of vegetable oils or of fat acids.
 9. A process according toclaims 1, wherein the surfactant is ethoxylated tallow amine, havinggeneral formulaR—N(CH₂CH₂O)H_(m)(CH₂CH₂O)H_(n) with R=saturated alkyl chain having16-18 carbon atoms.
 10. A process according to claims 1, wherein thestep d) is carried out under stirring with a higher intensity than thatof step c), preferably in a mixer, optionally equipped with chopper,working at a rate between about 80 and 120 rpm.
 11. A process accordingto claim 10, wherein the mixer choppers are used.
 12. A processaccording to claims 1, wherein the extrusion of step e) is carried outby low pressure extruders, preferably basket extruders.
 13. A processaccording to claims 1, wherein the drying of step f) is carried out influid bed dryers, preferably at temperatures in the range 70° C.-120°C., more preferably 80° C.-100° C.
 14. A process according to claim 13,wherein the time used for drying ranges from 10 to 15 minutes. 15.Granules of monoammonic glyphosate obtainable by the process ofclaims
 1. 16. Granules according to claim 15, wherein the content ofequivalent glyphosate acid is higher than or equal to 48% by weight. 17.Granules according to claims 15, wherein the surfactant content isbetween 5% and 25% by weight.
 18. Granules according to claims 15,wherein the surfactant content is between 10% and 20% by weight.